Modern aircrafts accommodate onboard a plurality of 3-phase AC motors which are used to power various facilities onboard of the aircraft, such as fans or ventilators of the air conditioning system which are located in different sections of the cabin, cock-pit, sanitary rooms, cargo compartment or in other areas of the aircraft. A ventilator is normally powered by a 3-phase AC motor. A thermal circuit breaker is accommodated inside the 3-phase AC motor which ensures that the 3-phase AC motor is automatically switched off upon, for example, overheating of the motor windings.
It is important that these 3-phase motors operate correctly, turn in the correct direction and that its safety devices and protections operate correctly as designed. Therefore, during final assembly and after repair or modification of the aircraft, tests are to be performed to verify correct connection and operation of the 3-phase equipment.
One of these tests includes testing the electronic control circuitry onboard of the aircraft in terms of proper functioning of all motors. In the course of these tests, the components and the control logic upstream of the 3-phase AC motors is checked. To this end, the 3-phase AC motors are disconnected prior to performing the tests.
The objective of these tests is to ensure that all terminals (to which the 3-phase AC motor is connected for powering e.g. the ventilators) are present and the correct voltage is applied to the terminals. Secondly, the phase difference of the voltages between the three terminals is verified. In other words, it is to be checked whether the phase on each terminal is as specified, e.g. the phase difference being equal 120°. In addition, it must be inspected whether upon initiation of the thermal circuit breaker, a corresponding warning signal is sent to an indicator which, for example, is located inside the cockpit of the aircraft, and thus visible to the pilot. The warning signal then alerts the pilot that one of the 3-phase AC motors is overheated and therefore automatically switched off.
Up to date, the staff conducting the maintenance or production tests and inspections had to manually check each terminal in terms of correct voltage and correct phase difference. An initiation of the thermal circuit breaker had to be manually simulated in order to test whether initiation of the thermal circuit breaker effected output of a corresponding warning signal (e.g. “motor overheated” or “motor failure”) to the cockpit of the aircraft. Thus, these tests and inspections required much manpower and many different test tools and were cost-intensive.
It is therefore an object of the invention to provide a method and a kit for testing power lines and signal lines onboard of an aircraft which considerably facilitate the ground tests of an aircraft. In particular, the present invention provides a method and a kit for testing power lines and signal lines to and from 3-phase AC motors installed onboard of the aircraft in terms of correct voltage and correct phase difference.